The simulation of joint is pivotal for car body structural analysis in concept design phase. The detail simulation method was implemented by solving the detail joint model using non-decoupling method. The detail information was afforded about joint detail modeling and the process of non-decoupling. The process of solving the parameters of joint was also described with equations. By the solved parameter values, the joint concept was built with ball hinge elements and spring elements. At last, a comparison between concept model with detail joint simulation and detail model of car body shows that the detail simulation method in this paper is feasible and accurate.